1. Field of the Invention
The present invention is concerned with the field of breathing masks and in particular with aircraft flight crew oxygen masks.
2. Description of the Prior Art
Most aircraft flight crew oxygen masks include a demand breathing regulator and a microphone. To communicate with other crew members or with the control tower, for example, the wearer of a prior art mask activates the microphone which converts received sounds into audio signals for transmission. The sounds received by the microphone include not only the wearer's voice, lude not only the wearer's voice, but background noise as well. When the wearer is inhaling, the sound of gas flow through the mask's breathing regulator is often particularly loud and is transmitted as noise having a large component comparable in both frequency and intensity to the sounds made by a person speaking. When two or more members of a flight crew are wearing masks at the same time and one of the crew members is speaking, the noise generated during inhalation by the others can seriously interfere with hearing or understanding the voice transmission of the crew member who is speaking.
As can be appreciated, this can present a very serious situation because usually two or more crew members are not on oxygen unless a flight problem has developed. In such circumstances, clear communications are especially important, but are the very circumstances that present the greatest interference with communications. Electronic filtering or dampening cannot be used without also filtering the sounds of speech. Accordingly, the prior art points out the need for a microphone equipped breathing mask that does not interfere with communications.